$ { {-5} \times \left[\begin{array}{rrr}{1} & {-2} & {4} \\ {1} & {-2} & {0}\end{array}\right] = {?} } $
Answer: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rrr}{-5}\times{1} & {-5}\times{-2} & {-5}\times{4} \\ {-5}\times{1} & {-5}\times{-2} & {-5}\times{0}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{-5} & {10} & {-20} \\ {-5} & {10} & {0}\end{array}\right]}$